Mycelium-Based Composites in Art, Architecture, and Interior Design: A Review

Mycelium-based composites (MBCs) have attracted growing attention due to their role in the development of eco-design methods. We concurrently analysed scientific publications, patent documents, and results of our own feasibility studies to identify the current design issues and technologies used. A literature inquiry in scientific and patent databases (WoS, Scopus, The Lens, Google Patents) pointed to 92 scientific publications and 212 patent documents. As a part of our own technological experiments, we have created several prototype products used in architectural interior design. Following the synthesis, these sources of knowledge can be concluded: 1. MBCs are inexpensive in production, ecological, and offer a high artistic value. Their weaknesses are insufficient load capacity, unfavourable water affinity, and unknown reliability. 2. The scientific literature shows that the material parameters of MBCs can be adjusted to certain needs, but there are almost infinite combinations: properties of the input biomaterials, characteristics of the fungi species, and possible parameters during the growth and subsequent processing of the MBCs. 3. The patent documents show the need for development: an effective method to increase the density and the search for technologies to obtain a more homogeneous internal structure of the composite material. 4. Our own experiments with the production of various everyday objects indicate that some disadvantages of MBCs can be considered advantages. Such an unexpected advantage is the interesting surface texture resulting from the natural inhomogeneity of the internal structure of MBCs, which can be controlled to some extent.


Introduction
Fungi can use many types of by-products as substrates for growth. When mycelium penetrates a substrate, it acts as a natural self-assembling binder, holding a loose mixture in a monolithic form, creating a solid composite of biopolymers cellulose matrix and very dense chitin reinforcement. Mycelium can fill the volume with a very dense network; one gram of soil can contain up to 600 km of hyphae [1]. The mycelium growth pattern is related to the availability of food resources, water and environmental conditions, which constantly modify the network topology. The adaptive behaviour of fungi allows them to cope with various ephemeral resources, competition, damage, and predation in a completely different manner from multicellular plants or animals [2]. In nature, the organic matter for fungal growth comes from the remains of plant and animal organisms and their metabolites. In industrial conditions, various types of biological post-consumer wastes and by-products Over 130 different "author keywords" are used in the articles. Associations and frequency of co-existence for 20 most frequently used "author keywords" are shown in Figure 2.
In the Figure 2, the frequency of occurrence of the keywords varies with time in color. VOSviewer was used; minor editorial changes have been made in the keywords: singular and plural forms of nouns ("fungus" = "fungi", "material" = "materials" etc.), the notation ("bio-composites" = "biocomposites" etc.), synonyms ("fungal mycelium" = "mycelium", "composite materials" = "composites", "bio-based composites" = "biocomposites" and "manufacturing process" = "manufacture"). Yellow color, turning red, indicates keywords used in the most recent articles. As can be seen, these are the words "sustainable development", "scanning electron microscopy", "construction industry" and "agricultural robots". This shows the changing research interests in this field.
The five most cited articles according to Scopus are summarized in Table 1.   Over 130 different "author keywords" are used in the articles. Associations and frequency of co-existence for 20 most frequently used "author keywords" are shown in Figure 2. Over 130 different "author keywords" are used in the articles. Associations and frequency of co-existence for 20 most frequently used "author keywords" are shown in Figure 2.
In the Figure 2, the frequency of occurrence of the keywords varies with time in color. VOSviewer was used; minor editorial changes have been made in the keywords: singular and plural forms of nouns ("fungus" = "fungi", "material" = "materials" etc.), the notation ("bio-composites" = "biocomposites" etc.), synonyms ("fungal mycelium" = "mycelium", "composite materials" = "composites", "bio-based composites" = "biocomposites" and "manufacturing process" = "manufacture"). Yellow color, turning red, indicates keywords used in the most recent articles. As can be seen, these are the words "sustainable development", "scanning electron microscopy", "construction industry" and "agricultural robots". This shows the changing research interests in this field.
The five most cited articles according to Scopus are summarized in Table 1.   In the Figure 2, the frequency of occurrence of the keywords varies with time in color. VOSviewer was used; minor editorial changes have been made in the keywords: singular and plural forms of nouns ("fungus" = "fungi", "material" = "materials" etc.), the notation ("bio-composites" = "biocomposites" etc.), synonyms ("fungal mycelium" = "mycelium", "composite materials" = "composites", "bio-based composites" = "biocomposites" and "manufacturing process" = "manufacture"). Yellow color, turning red, indicates keywords used in the most recent articles. As can be seen, these are the words "sustainable development", "scanning electron microscopy", "construction industry" and "agricultural robots". This shows the changing research interests in this field.
The five most cited articles according to Scopus are summarized in Table 1.
There are different purposes for the research carried out. The vast majority of research focuses on finding out how to properly shape the constructional properties of the material. The objectives and results of selected research works on mycelium-based composites are collected in Table 2. In 2016-2021, at least 20 scientific review articles were also published. The most important of these articles are listed in Table 3. The process of engineering affects the properties of MBCs. Bioreactor designs such as tray, packed bed and millilitre reactors, influence of mycelium growth conditions and strategies for controlling mycelium microenvironment are discussed to allow optimal process development.

2021
[102] 118 0 1. MBCs are advantageous as packaging materials with sufficient acoustic, and thermal insulation, slightly worse than expanded polystyrene. 2. The standardized process to produce an optimized material property has yet to be identified, production is less standardized than conventional engineering materials, and it is not clear how to customize the substrates for a particular species of fungi to optimize the composite mechanics.

Results of Patents Documents Analysis
A granted patent is an administrative decision: area and time limited, issued by the patent office, it provides protection for a feasible, new, non-obvious and potentially profitable solution. The basis for such a decision is a patent application, which requires an unambiguous description of the essence of the invention. The patent application also provides a priority date, i.e., the date of disclosure of the invention. The priority date can, for example, be the presentation of the invention at a trade fair or the publication of a description of the invention. Most often, however, it is the date when the invention is filed with the patent office. Some patent applications become granted patents. Inventions considered profitable by their owners are filed in many patent jurisdictions around the world. Subsequent applications may differ slightly from their prototypes in terms of content, the differences result mainly from the refinement of descriptions, as well as the rejection of some patent claims by various patent offices. The main patent documents are patent applications and granted patents from many patent offices, they form the so-called patent families. Thus, each patent family describes one invention, the date of its creation is given by its first application.
Patent documents were searched on the basis of the following keywords: mycelium; mycological; fungi; biopolymers; biomaterials; biocomposites. These words were searched for in the "TAC" sections of patent documents (TAC = title OR abstract OR claim). Searches were made in the International Patent Classification areas: C08*, C12N*, B27N* B32B* oraz B32B*, and the list of documents was reviewed, limiting it to issues related to the production of plastics such as foams, boards and blocks used in construction, furniture, the automotive industry, as packaging and as artistic products. Thus, documents dealing with the production of woven fabric, i.e., all non-structural materials used in the manufacturing technique, were omitted. Publicly available databases and analytical tools such as Google Patents, The Lens were used, and the results of queries were exported to MS Excel for further analysis.
As a result of the analysis, 212 patent documents were identified: 153 patent applications, 55 patents granted on the basis of some of these applications, and additionally 2 amended applications, 1 amended patent and 1 patent of addition. They constitute 67 extended families, and thus describe 67 different technological and product inventions related to mycelium-based composites. The oldest document was received by the United States Patent and Trademark Office on 12 December 2007 [106], while the last of the analysed documents was on 9 April 2021 [107]. The annual numbers of patent applications, according to the years of their publication, are shown in Figure 3.  Data for 2021 is incomplete, not all patent documents from this year are indexed in databases. The data on the annual number of patents presented in Figure 3 show a significant increase in patent applications in the last two years.
There are significant 9 people and organizations among the owners of patent documents. This is shown in Figure 4 as shares in overall number of patent documents.  Data for 2021 is incomplete, not all patent documents from this year are indexed in databases. The data on the annual number of patents presented in Figure 3 show a significant increase in patent applications in the last two years.
There are significant 9 people and organizations among the owners of patent documents. This is shown in Figure 4 as shares in overall number of patent documents. Data for 2021 is incomplete, not all patent documents from this year are indexed in databases. The data on the annual number of patents presented in Figure 3 show a significant increase in patent applications in the last two years.
There are significant 9 people and organizations among the owners of patent documents. This is shown in Figure 4 as shares in overall number of patent documents. The analysis of patent documents shows 9 main countries related with the myceliumbased composites ( Figure 5). The largest number of affiliated patent documents is in the USA. However, the latest documents are affiliated in Germany, Belgium and China.  The analysis of patent documents shows 9 main countries related with the myceliumbased composites ( Figure 5). The largest number of affiliated patent documents is in the USA. However, the latest documents are affiliated in Germany, Belgium and China. In 29 patent families there is at least one granted patent, these familie summarized in Table 4, presenting one selected patent from each such patents famil  In 29 patent families there is at least one granted patent, these families are summarized in Table 4, presenting one selected patent from each such patents family. More than 200 patent documents make it impossible to "intuitively" indicate the key inventions in the field of mycelium-based composites. Undoubtedly, the first patent application (US 2008/0145577 A1, "Method for producing grown materials and products made thereby" [106], filing date 12 December 2007) is important, but there are likely to be other influential inventions in this field. In the 2019 scientific article on the review of wood screw patents [136], the following criteria were proposed for the identification of important patents:

•
The size of the patent family-the assumption: "only an invention with high application potential can be submitted for protection in many patent offices because the patent procedure is paid". • Number of citations of a patent document in other, later patent documents-the assumption: "if multiple patent documents refer to a particular document, it indicates that this document describes (and perhaps at least partially solves) a significant problem.
Using these two criteria, the most influential patent documents for mycelium-based technology were listed in Table 5. The generalized MBCs production protocol can be compiled from research articles, patent documents, or open source manuals (e.g., [142]). Such a general protocol includes: (1) The chosen mycelium specie is pre-grown in a Petri dish with a growth medium solidified with agar. (2) The substrate for the culture of mycelium is homogenized (the substrate is a mix of selected biopolymers with defined granulation and proportion). The substrate is also sterilized to kill or deactivate all microorganisms in it. (3) The pre-grown mycelium and sterile water are added to the substrate. Additional nutrients can also be added. The inoculated substrate is packed in a sterile mould (a bag or a container). (4) The mycelium grows trough the substrate in a controlled micro-climate (temperature, air humidity, without light). The mycelium composite can be created initially in the mould to its internal reinforcement, and then outside the mould to solidify its surface. (5) The mycelium composite is sterilized to end the growth process and then dried to the target moisture content. (6) A pressing, machining, coating or other required product post-processing is applied.
The review of patent documents shows that biofoam composites and layered structures with mycelium-based composites can be used in building structures as structural materials (e.g., the core of sandwich panels and gap fillers), interior finishing materials (e.g., wall panels) and floors), as well as materials for portable home furnishings (furniture and other portable items) and packaging materials. They can have an insulating function due to their low heat conductivity or a sound-absorbing function. Biocomposites can therefore be an alternative to synthetic foams found in automotive bumpers, doors, roofs, engine cavities, boot linings, dashboards, and seats because the mycelium-based material has the same or better ability to absorb impacts, insulate, dampen sound and provide lightweight construction in the car from typical synthetic foams. The material also showed good fire resistance. Applications in the construction industry are mainly limited to fire-proof thermal and acoustic insulators. So far, the use of this innovative biocomposite in the construction industry has been limited only to a small scale and to exhibition installations.
Considering all the ecological advantages of mycelial and bio-substrate composites, the question arises, why such materials are not used very widely. Potential reasons for this may be problems with low mechanical properties, high water absorption, lack of Life Cycle Assessment information for this material, and lack of standard production methods and standardized methods for testing material properties.

Mycelium-Based Material in Elements of Interior Design-Case Study
Even though the mycelium-based composites is currently studied mostly for purposes in which visual or aesthetical aspects are insignificant, like packaging, experiments performed by the authors suggest that it can be successfully used for creating interior design elements. Mycelium-based materials embrace a new aesthetics characterized by imperfections and irregularities through natural and spontaneous growth, thus achieving a unique structure, as in wood. The physical and geometric properties of objects evolve and change slightly over time. These properties make it an unusual and challenging material. Different textures that characterize the material samples depend on how the substrate has been formed before the growth; the material's surface has visible natural fibres and dominating natural mycelium colouring: off-whites with yellow or brownish irregularities in more mature areas. The user perceives these characteristics as organic, warm, and natural, which influences the typology of products that could be created.
The first shapes obtained from mycelium-based material by Agata Bonenberg were simple panels that allowed the growth and maturation of the material to be observed (Figures 6 and 7). Then spherical objects were created to study the emergence of different textures: smooth (Figure 8), rough (Figure 9). The object shown in Figure 10 combines both; it has a smooth well-fragmented substrate at the bottom, and an uneven, rough part at the top. This opens interesting possibilities for future projects.
Polymers 2022, 14, x FOR PEER REVIEW Cycle Assessment information for this material, and lack of standard production m and standardized methods for testing material properties.

Mycelium-Based Material in Elements of Interior Design-Case Study
Even though the mycelium-based composites is currently studied mo purposes in which visual or aesthetical aspects are insignificant, like pa experiments performed by the authors suggest that it can be successfully used for interior design elements. Mycelium-based materials embrace a new a characterized by imperfections and irregularities through natural and spon growth, thus achieving a unique structure, as in wood. The physical and ge properties of objects evolve and change slightly over time. These properties ma unusual and challenging material. Different textures that characterize the samples depend on how the substrate has been formed before the growth; the m surface has visible natural fibres and dominating natural mycelium colouring: of with yellow or brownish irregularities in more mature areas. The user perceiv characteristics as organic, warm, and natural, which influences the typology of p that could be created.
The first shapes obtained from mycelium-based material by Agata Bonenbe simple panels that allowed the growth and maturation of the material to be o (Figures 6 and 7). Then spherical objects were created to study the emergence of d textures: smooth (           Experimentation with textures and shapes of forms has led to preliminary development and production. The designs of a table light fixture, a table bowl, and table have been executed. In each of these projects, mycelium-based elements h combined with other materials. The author has chosen natural components such a to match the design's pro-ecological spirit and give overall natural "touch". Th table lamp is a good example of this approach: a mycelium-grown, cylindrical lam has been fixed on a simple cubical timber base (Figures 11 and 12). Experimentation with textures and shapes of forms has led to preliminary product development and production. The designs of a table light fixture, a table bowl, and a coffee table have been executed. In each of these projects, mycelium-based elements had to be combined with other materials. The author has chosen natural components such as timber to match the design's pro-ecological spirit and give overall natural "touch". The small table lamp is a good example of this approach: a mycelium-grown, cylindrical lampshade has been fixed on a simple cubical timber base (Figures 11 and 12). Similarly, a container bowl was created, where an upper part of the object was fixed to the rough-timber torus-shaped base (Figures 12 and 13). Again, the look of the object is "organic". At the same time, the heavier wooden base gives the bowl its functional stability. Similarly, a container bowl was created, where an upper part of the object w to the rough-timber torus-shaped base (Figures 12 and 13). Again, the look of the "organic". At the same time, the heavier wooden base gives the bowl its fu stability.  Similarly, a container bowl was created, where an upper part of the object was fixed to the rough-timber torus-shaped base (Figures 12 and 13). Again, the look of the object is "organic". At the same time, the heavier wooden base gives the bowl its functional stability. Another artifact created is a coffee table where a mycelium-based tabletop h grown on a metal frame, ensuring its structural stability ( Figure 14). The tabletop but light, with well-consolidated smooth surfaces from the top and sides, but an and rough texture can be perceived from the bottom. In addition, there is a clear between the thin steel legs of the table and the thick-bodied top. Finally, the tr shape gives the object expressive, characteristic looks. Another artifact created is a coffee table where a mycelium-based tabletop has been grown on a metal frame, ensuring its structural stability ( Figure 14). The tabletop is thick but light, with well-consolidated smooth surfaces from the top and sides, but an uneven and rough texture can be perceived from the bottom. In addition, there is a clear contrast between the thin steel legs of the table and the thick-bodied top. Finally, the triangular shape gives the object expressive, characteristic looks.
Another artifact created is a coffee table where a mycelium-based tabletop has been grown on a metal frame, ensuring its structural stability ( Figure 14). The tabletop is thick but light, with well-consolidated smooth surfaces from the top and sides, but an uneven and rough texture can be perceived from the bottom. In addition, there is a clear contrast between the thin steel legs of the table and the thick-bodied top. Finally, the triangular shape gives the object expressive, characteristic looks. The challenge of unconventional materials is the technique of fastening elements [143,144]. The new material requires a new approach in this field, which will be a further direction of our activities.

Conclusions
Regarding the current excessive dependence of the construction and production industry on hydrocarbon-containing materials occurring within Earth's crust; taking into account the abundance of waste and industrial by-products, it is necessary to make greater use of the advantages of biomaterials with a low carbon footprint [145][146][147][148][149][150][151][152]. The following conclusions can be drawn from the reviewed content presented: The challenge of unconventional materials is the technique of fastening elements [143,144]. The new material requires a new approach in this field, which will be a further direction of our activities.

Conclusions
Regarding the current excessive dependence of the construction and production industry on hydrocarbon-containing materials occurring within Earth's crust; taking into account the abundance of waste and industrial by-products, it is necessary to make greater use of the advantages of biomaterials with a low carbon footprint [145][146][147][148][149][150][151][152]. The following conclusions can be drawn from the reviewed content presented:

1.
MBCs (mycelium-based composites) offer favourable production price, ecological value, and high artistic value. Their weaknesses are insufficient design properties and not fully known reliability (quality during use), therefore both scientific research and engineering creativity, which is manifested by patents documents, are heading in this direction.

2.
A review of the scientific literature shows that the material parameters of MBCs can be adjusted to the needs: by selecting the type of substrate and fungus species, by controlling the growth conditions, the method of inactivation of the mycelium after growth, and the drying method. In this way, it is possible to meet certain requirements, e.g., increase the structural load-bearing capacity to an acceptable level and reduce the affinity with water, and additionally improve the acoustic and thermal insulation. However, the problem is the almost infinite number of combinations: properties of the input biomaterials, characteristics of the mushroom species, and parameters during growth and subsequent processing of the MBC.

3.
The review of patent documents shows that two current technological challenges are related to the creation of MBCs with the properties required by the final product. Especially, looking for an effective method of increasing strength, for example by increasing the density, the search for a method of obtaining a more homogeneous internal structure. 4.
The described own technological experiments, consisting of the production of various everyday objects, indicate that some disadvantages of MBCs can be considered advantages. Such an unexpected advantage is the interesting and unrepeatable surface texture resulting from the natural unevenness of the internal structure of MBCs, which can be controlled to some extent.
The presented results of the analysis of a wide variety of literature and own technological experiments suggest that the share of mycelium-based composites in industrial production and construction will increase, despite certain limitations of this innovative